My 9 month old entire male pug has just started cocking his leg on people at the park, and I really need to stop this behaviour now before it becomes a habit. I'm hoping someone can point me in the right direction with this. His training is going well apart from this, no humping issues and he comes back to the whistle when out so his recall is very good. Hope someone can help I would be very grateful for any advice.

Use a long line so you can pull him away before he has a chance to do this. 

A sharp 'ahah', as soon as he looks like he might try to lift his leg near a person.

Boys are horrible aren't they. This is one of the very few times where a good sharp verbal telling off can be very useful, though reward based training is best 99% of the time. My first boy cocked his leg up me at about 12 months old and I caught him in the act, got down face to face and really yelled at him for some minutes!! Didn't stop to think about whether it was right or not, and perhaps it's not right for all dogs, I'm no expert. But I know that he never cocked his leg on me or anyone else ever again. Never cocked his leg indoors even if girls were in season. Never cocked his leg on anyone bag or belongings at stalls at shows. He just somehow knew that it was totally unacceptable from then on. He did still cock his leg on bushes and lampposts perfectly happily, but had somehow made the connection on what was ok and what wasn't.

Thank you for the replies I feel silly asking now as the answer is obvious really lol. Think I was just shocked he done it, I have kept a very close eye on him, there's not many people up the country park at the moment as it very muddy. Lucydogs I think I would have done the same as you if I wasent shocked, and it worked so it was the right thing for your dog. I will put him on an extending lead if I have to but obviously I want to teach him it's wrong.

Well it obviously wouldn't be good if you had a nervous dog or something - but for a supremely confident bolshy young oik it was just the thing!

> I will put him on an extending lead if I have to ......

I think you need to have him close by you, not on an extending lead (extended!).   With these leads, extended, you won't have the same control over what he's up to as you would have on a sensible lead - no longer than 5 foot.   Ditto for a long line in my opinion.   He'll have done this before you'd be able to haul him off - surely?   And how you react would depend on how sensitive the dog is - if I yelled at my male(s) I'd demolish them.

Oh absolutely, not the right approach for a sensitive dog at all. My boy was as far from sensitive as you could possibly be bless him.